Chromosomal mapping of rDNAs, core histone genes and telomeric sequences in Perumytilus purpuratus (Bivalvia: Mytilidae)

A tandemly repeated unit of 6553 bp containing a copy of the four core histone genes H2B, H2A, H3, and H4, and also a 5S rRNA gene, was amplified by PCR from genomic DNA of the isopod crustacean Asellus aquaticus. The linkage between 5S rRNA genes and histone genes has been so far observed in only one other organism, the anostrac crustacean Artemia salina. The gene cluster was cloned and sequenced. The histone genes, in their 3' flanking region, have the interesting feature of possessing two different mRNA termination signals, the stem-loop structure and the AATAAA sequence. A part of the PCR product was used as a probe in FISH experiments to locate the gene cluster on an inter-individually variable number of chromosomes from 6 to 12 per diploid cell, always in a terminal position and never associated with the heterochromatic areas. Fluorescence in situ hybridization (FISH) was also performed on preparations of released chromatin and the reiteration level of the gene cluster was determined as approximately 200-300 copies per haploid genome. Key words: Asellus, Isopoda, Crustacea, histone genes, 5S rRNA gene.

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Cytogenetic characterization of the invasive mussel species Xenostrobus securis Lmk. (Bivalvia: Mytilidae)

Genome ◽

10.1139/g11-040 ◽

2011 ◽

Vol 54 (9) ◽

pp. 771-778 ◽

Cited By ~ 14

Author(s):

Concepción Pérez-García ◽

Paloma Morán ◽

Juan J. Pasantes

Keyword(s):

5S Rdna ◽

Gene Clusters ◽

Linker Histone ◽

Histone Gene ◽

Core Histone ◽

Histone Genes ◽

Single Chromosome ◽

Telomeric Sequences ◽

Xenostrobus Securis ◽

Dapi Fluorescence

The chromosomes of the invasive black-pigmy mussel (Xenostrobus securis (Lmk. 1819)) were analyzed by means of 4’,6-diamidino-2-phenylindole (DAPI) / propidium iodide (PI) and chromomycin A3 (CMA) / DAPI fluorescence staining and fluorescent in situ hybridization using major rDNA, 5S rDNA, core histone genes, linker histone genes, and telomeric sequences as probes. The diploid chromosome number in this species is 2n = 30. The karyotype is composed of seven metacentric, one meta/submetacentric, and seven submetacentric chromosome pairs. Telomeric sequences appear at both ends of every single chromosome. Major rDNA clusters appear near the centromeres on chromosome pairs 1 and 3 and are associated with bright CMA fluorescence and dull DAPI fluorescence. This species shows five 5S rDNA clusters close to the centromeres on four chromosome pairs (2, 5, 6, and 8). Three of the four core histone gene clusters map to centromeric positions on chromosome pairs 7, 10, and 13. The fourth core histone gene cluster occupies a terminal position on chromosome pair 8, also bearing a 5S rDNA cluster. The two linker histone gene clusters are close to the centromeres on chromosome pairs 12 and 14. Therefore, the use of these probes allows the unequivocal identification of 11 of the 15 chromosome pairs that compose the karyotype of X. securis.

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Sex Chromosomes and Internal Telomeric Sequences in Dormitator latifrons (Richardson 1844) (Eleotridae: Eleotrinae): An Insight into Their Origin in the Genus

Genes ◽

10.3390/genes11060659 ◽

2020 ◽

Vol 11 (6) ◽

pp. 659

Author(s):

Fabilene Gomes Paim ◽

Mauro Nirchio ◽

Claudio Oliveira ◽

Anna Rita Rossi

Keyword(s):

Sex Chromosomes ◽

Food Resource ◽

5S Rdna ◽

Molecular Techniques ◽

Chromosomal Mapping ◽

Nucleolar Organizer Regions ◽

Neotropical Fish ◽

Telomeric Repeats ◽

Western Atlantic ◽

Telomeric Sequences

The freshwater fish species Dormitator latifrons, commonly named the Pacific fat sleeper, is an important food resource in CentralSouth America, yet almost no genetic information on it is available. A cytogenetic analysis of this species was undertaken by standard and molecular techniques (chromosomal mapping of 18S rDNA, 5S rDNA, and telomeric repeats), aiming to describe the karyotype features, verify the presence of sex chromosomes described in congeneric species, and make inferences on chromosome evolution in the genus. The karyotype (2n = 46) is mainly composed of metacentric and submetacentic chromosomes, with nucleolar organizer regions (NORs) localized on the short arms of submetacentric pair 10. The presence of XX/XY sex chromosomes was observed, with the X chromosome carrying the 5S rDNA sequences. These heterochromosomes likely appeared before 1 million years ago, since they are shared with another derived Dormitator species (Dormitator maculatus) distributed in the Western Atlantic. Telomeric repeats hybridize to the terminal portions of almost all chromosomes; additional interstitial sites are present in the centromeric region, suggesting pericentromeric inversions as the main rearrangement mechanisms that has driven karyotypic evolution in the genus. The data provided here contribute to improving the cytogenetics knowledge of D. latifrons, offering basic information that could be useful in aquaculture farming of this neotropical fish.

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H2B Tyr37 phosphorylation suppresses expression of replication-dependent core histone genes

Nature Structural & Molecular Biology ◽

10.1038/nsmb.2356 ◽

2012 ◽

Vol 19 (9) ◽

pp. 930-937 ◽

Cited By ~ 59

Author(s):

Kiran Mahajan ◽

Bin Fang ◽

John M Koomen ◽

Nupam P Mahajan

Keyword(s):

Core Histone ◽

Histone Genes

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Individual regulation of the accumulation of H1 mRNA and core histone mRNAs in sea urchin embryos.

Molecular and Cellular Biology ◽

10.1128/mcb.3.6.974 ◽

1983 ◽

Vol 3 (6) ◽

pp. 974-981 ◽

Cited By ~ 1

Author(s):

E J Baker ◽

A A Infante

Keyword(s):

Sea Urchin ◽

Sea Urchins ◽

Core Histone ◽

Molar Ratio ◽

Histone Genes ◽

Mrna Accumulation ◽

The Core ◽

Histone Mrnas ◽

The Individual

The relative cytoplasmic accumulation of the individual histone mRNAs in sea urchins was determined by gel analysis of 3H-labeled cytoplasmic RNA isolated from embryos of the early cleavage through the mesenchyme blastula stages. A number of separate determinations showed that H1 mRNA accumulates at a molar ratio of 0.5 or less compared with each of the H2 or H3 core histone mRNAs through approximately the first 12 h of embryonic development. After this time, the accumulation of H1 mRNA increases relative to the core histone mRNAs, and approximately equimolar amounts of the histone mRNAs are produced by about the 14-h stage. The equimolar synthesis of H1 mRNA appears to be transient, returning to 0.5-molar levels several hours later. The increase in H1 mRNA accumulation, relative to the core histone RNAs, is coincident with the transition from expression of the early (alpha) sea urchin histone gene set to the late histone genes. Since all five of the early histone genes occur in a 1:1 ratio within repeating units, the data suggest that the genes within a single repeat, or their immediate products, are individually regulated. Gel analysis of the proteins synthesized in vivo by embryos demonstrates that the pattern of synthesis of the histone proteins reflects the changing ratios of the histone mRNAs.

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